Question

1.For the three Chloro-alkali cells do chemical equations, cathode, anode.

Answer 1

Three chloro- alkali cells are:

a) Mercury cell

b) Diaphragm cell

c) The Membrane cell

a) In Mercury cell :

Anode used : Carbon electrode

Oxidation takes place as follows:

2Cl^- (aq) Cl₂ (g) + 2e-

Cathode used : mercury( Hg)

Here Na⁺ undergo reduction to sodium amalgam

Na⁺ + e- NaHg

This sodium amalgam reacts with water as follows:

NaHg + H₂O NaOH + H₂ + Hg

b)Diaphragm cell

Here brine solution is taken in electrolytic cell contain cathode and anode compartments separated by diaphragm consist of porous asbestos to separate the NaOH and Cl₂ formed.

At anode : Cl^- Cl₂ + 2e-

At cathode: Na⁺ +H₂O NaOH + H₂

c) Membrane cell: Here In place of diaphragm , membrane is used which is selective to cation means only cation can pass through it.

In anode compartment brine solution is taken, and pure water is taken in cathode compartment

At anode Cl^- Cl₂ + 2 e-

Na+ moves into cathode containing pure water in which following reaction occur:

Na⁺ + H₂O NaOH + H₂